1. Technical Field of the Invention
The present invention relates to safety closures for use on containers. More particularly, the present invention relates to a safety closure for use on a container wherein the safety closure is provided with enhanced retaining means.
2. Discussion of the Prior Art
It is often desirable to provide a fluid-impervious seal between a container and a safety closure fitted thereupon, such as, for example, when the container is filled with a liquid. However, it is often difficult to provide an efficient fluid-impervious seal between the container and the safety closure due to an imperfect fit therebetween. It is thus desirable to provide a safety closure for use on a container wherein the safety closure provides an enhanced seal therebetween.
It is well known in the prior art to dispose a flexible gasket within the safety closure, and more particularly, within an inner region of the safety closure engageable with an upper terminal end of the container neck. Fitting the safety closure upon the container neck, such as, for example, by threading, forces the upper terminal end of the container neck to sealingly engage a lower surface of the flexible gasket, which receives the upper terminal end of the container neck and provides a fluid-impervious seal therebetween. However, even nominal unthreading of the safety closure from the container neck causes the upper terminal lip of the container neck to be drawn downwardly away from the flexible gasket, thereby breaking the sealing contact therebetween. This situation is even more severe for other means of fitting the safety closure upon the container neck, such as, for example, by a snap bead, which often results in a great deal of potential for relative axial movement between the upper terminal end of the container neck and the safety closure before the safety closure is removed therefrom. It is therefore desirable to provide a safety closure for use on a container wherein the safety closure is provided with sealing means, such as, for example, an integral sealing gasket, therein to engage the upper terminal end of the container neck.
Various attempts have heretofore been made to provide a safety closure having a sealing gasket disposed therein. For example, U.S. Pat. No. 4,138,028 to Price, et al., teaches a safety closure having a sealing liner to provide sealing contact with an upper terminal end of a container neck, as well as an annular retaining flange for secondary sealing contact with an outer annular surface of the container neck. However, it is further desirable to provide a safety closure for use on a container wherein the safety closure is provided with means for maintaining a sealing engagement therebetween.
For example, U.S. Pat. No. 2,752,060 to Martin teaches a container closure having a flange engageable with an annular shoulder provided on a container neck, wherein the flange and the shoulder cooperate to provide a continuous sealing force between an upper terminal edge of the container neck and a gasket provided on an underside surface of the container closure. Until the present invention, however, use of such a retaining flange to maintain a continuous sealing force between the container neck and the gasket has been limited to closures having only a single annular shell. For those so-called "double-shelled closures" wherein the closure is provided with a concentric inner annular shell in addition to an outer annular shell, the geometry of the molding dies typically used in forming same often result in a rigid flange being incapable of removal from the molding die. As such, manufacturing of a double-shelled closure having a retaining flange provided on the inner annular shell required expensive equipment and complicated manufacturing processes. It is therefore desirable to provide a double-shelled safety closure for use on a container wherein a continuous sealing force is provided between the container and the safety closure by means of a flexible retaining flange provided on an inner annular shell of the closure.